Crystal structure of caesium dimethyl-N-benzoylamidophosphate monohydrate

The crystal structure of the caesium salt of dimethyl-N-benzoylamidophosphate is reported and discussed.


Chemical context
The carbacylamidophosphates {CAPh, compounds of general formula [RC(O)N(H)P(O)R 0 2 ]}, first introduced by Alexandr Kirsanov in the 1960s, have now become an intensively investigated class of ligands (Amirkhanov et al., 2014). The structures of the alkali metal salts of CAPh anions, important starting reagents for the synthesis of their transition-metal complexes, have been poorly studied to date. The sodium and potassium salts with 2,2,2-trichloro-N-(dimorpholinophosphoryl)acetamide (HCAPh 1 ) contain ligated water molecules and have general formulae Na 2 CAPh 1 2 Á2H 2 O and KCAPh 1 ÁH 2 O, respectively (Litsis et al., 2010(Litsis et al., , 2016. The sodium salt of dimethyl-N-benzoylamidophosphate NaCAPh 2 (Kariaka et al., 2019) and the alkali salts of dimethyl-Ntrichloracetylamidophosphate NaCAPh 3 , RbCAPh 3 (Trush et al., 2005) crystallize in a solvent-free form. In all of these compounds the CAPh ligands are coordinated to the metal ions in a bidentate manner (via the oxygen atoms of the phosphoryl and carbonyl groups) with the formation of sixmembered chelate metallocycles. In addition, the phosphoryl or the carbonyl oxygen atom or both usually bridge the cations. Caesium salts of CAPhs have not been reported to date and are of interest as possible dopants in oxide film materials for the improvement of their electric and electron functional characteristics (Vikulova et al., 2013). Because of this, an actual task is the search for caesium compounds satisfying metal-organic chemical vapor deposition requirements. The combination of caesium ions with bulky organic ligands may result in compounds with molecular crystal structures that possess sufficient volatility. Thus, crystalstructure investigations of caesium salts of CAPh anions are of high interest. Herein, we present the crystal structure of the caesium salt of dimethyl-N-benzoylamidophosphate.

Structural commentary
Similar to the sodium salt of dimethyl-N-benzoylamidophosphate (Kariaka et al., 2019) the title compound crystallizes in the monoclinic crystal system in the P2 1 /c space group and forms a 1D-polymeric structure (Fig. 1).
The asymmetric unit contains the Cs + and CAPh À ions and a water molecule (Fig. 2a). The oxygen atoms of the carbonyl and phosphoryl groups of the dimethyl-N-benzoylamidophosphate anions act as 2 -bridges between Cs + cations ( Fig. 1). Additionally, both of the methoxy groups are bound to the Cs + and one of them also acts as a 2 -bridge. Thus, one CAPh À anion is bound to four Cs + cations (Fig. 2b), and each Cs + cation links four ligand anions. Additionally, a water molecule acts as a 2 -bridge between two Cs + cations.

Figure 1
Polymeric chain of the title compound extending along the [001] crystallographic direction.

Figure 2
Representation of (a) the asymmetric unit of the title compound and (b) the coordination mode of L À .

Supramolecular features
Few intermolecular contacts are observed in the crystal structure of the title compound. There are O-HÁ Á ÁO hydrogen bonds between the water molecule and the carbonyl and phosphoryl oxygen atoms of the dimethyl-N-benzoylamidophosphate anion (Table 2). In addition, the water molecule participates in a C8-H8CÁ Á ÁO5 contact with the hydrogen atom of the methoxy group of the CAPh ligand. The H8CÁ Á ÁO5 distance is 2.56 Å . There are no intermolecular contacts between the CAPh ligands in the crystal structure of the title compound.

Hirshfeld surface analysis and finger print plots
For visualization of the intermolecular interactions in the crystal structure for the asymmetric unit of the title compound, the Hirshfeld surface (Fig. 3) and its corresponding two-dimensional fingerprint plots (Spackman & Jayatilaka, 2009) were calculated using CrystalExplorer17 (Turner et al., 2017). The dark-red spots on the surface, which correspond to the strongest contacts in the crystal structure of the title compound, are observed for the HÁ Á ÁO/OÁ Á ÁH hydrogen bonds between hydrogen atoms of the water molecule and the oxygen atoms of the carbonyl and phosphoryl groups of the CAPh. The lighter red spots observed near the Cs + cation and the methoxy groups correspond to CsÁ Á ÁO/OÁ Á ÁCs bonds, which are involved in CsÁ Á ÁO contacts and HÁ Á ÁO contacts with the water molecule. There are no red spots on the Hirshfeld surface near the phenyl ring.
The derived fingerprint plots show that HÁ Á ÁH contacts make the largest contribution to the Hirshfeld surface (42.2%) and the shortest of them are at d i = d e = 1.2 Å . The second largest contribution (19.3%) comes from the HÁ Á ÁO/OÁ Á ÁH contacts, which are the shortest in the title compound (d i + d e = 1.75 Å ). The CÁ Á ÁH/HÁ Á ÁC and CsÁ Á ÁO/OÁ Á ÁCs interactions make similar contributions to the surface at 14.3% and 12.9%, respectively. The shortest CÁ Á ÁH/HÁ Á ÁC contacts are at d i + d e = 2.8 Å . The shortest CsÁ Á ÁO/OÁ Á ÁCs contacts are at d i + d e = 3.07 Å . Among the interactions making the smallest contribution to the Hirshfeld surface of the title compound are the OÁ Á ÁO, CÁ Á ÁC, CsÁ Á ÁH and NÁ Á ÁH interactions.

Database survey
A search of the Cambridge Structural Database (CSD, Version 5.42, update of November 2020; Groom et al., 2016) for alkali metal salts of carbacylamidophosphates yielded ten hits. Six of them are sodium salts, three are potassium salts and one is a rubidium salt. No CAPh-based caesium salts have been reported to date. In all these reported salts, the carbacylamidophosphates are coordinated to the alkali metals in a bidentate chelating manner via the oxygen atoms of the phosphoryl and carbonyl groups. Additionally, in the majority of these salts, the phosphoryl or the carbonyl oxygen atom or both function as 2 -bridges. In the alkali metal salts of CAPhs that contain methoxy groups, one of the latter is involved in contacts with the metal. In alkali metal salts of CAPhs that contain the CCl 3 group, the latter can be also involved in the metal binding. Some CAPh-based salts also contain such additional ligands as water molecules, coordinated to the metal in a 2 -bridging manner, or crown ethers. The Hirshfeld surface mapped over d norm and two-dimensional fingerprint plots for the HÁ Á ÁH (42.2%), HÁ Á ÁO/OÁ Á ÁH (19.3%), CÁ Á ÁH/ HÁ Á ÁC (14.3%) and CsÁ Á ÁO/OÁ Á ÁCs (12.9%) interactions for the asymmetric unit of the title compound Table 2 Hydrogen-bond geometry (Å , ).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3

Funding information
Funding for this research was provided by: Ministry of Education and Science of Ukraine .

Aqua[dimethyl (N-benzoylamido-κO)phosphonato-κO]caesium
Crystal data Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )